A bit about the stuff I've done

Tuesday 9 October 2012

The woes of inline functions

OK; so I like inline fucntions really - especially in javascript. But now I am realising their evil intent after I spent a not insubstantial amount of time tracing a bug.
here is the scenario:
A simple method with tbh not a whole lot in it.
In fact the entire method is taken by a single if/else block. Regardless of the outcome of both if blocks it is necassary to call a method afterwards.
So obviously that call goes outside the if.
Normally that would be fine.
But in my case the else block contained an inline function used as a callback.
A callback that will occur some undetermined (but very small) amount of time after the if block has exited.
Of course I needed to wait until this callback had been executed before calling the final method.
function DoSomething() { if (condition) { DoOneThing(); } else { AsyncronuslyDoAnother(function (result){ DoSomethingWithTheResultWhenTheAsyncCallCompletes(); }); } DoFinalThing(); } Now the simple solution in this instance was to move the call to DoFinalThing() to be inside the if block, and also inside the anonymous callback function.
function DoSomething2() { if (condition) { DoOneThing(); DoFinalThing(); } else { AsyncronuslyDoAnother(function (result){ DoSomethingWithTheResultWhenTheAsyncCallCompletes(); DoFinalThing(); }); } } However in my case the problem only arose in the first place because I simply didn't notice the inline function when I added the call to DoFinalThing() and assumed that it was all just part of the else logic.
So additionally I removed the inline function and henceforth declare all such things to be evil!
(ok well not quite, but at least I am more wary now!)
function AsyncCallback(result) { DoSomethingWithTheResultWhenTheAsyncCallCompletes(); DoFinalThing(); } function DoSomething3() { if (condition) { DoOneThing(); DoFinalThing(); } else { AsyncronuslyDoAnother(AsyncCallback); //N.B. no parens on AsyncCallback - we are passing a reference to the method not invoking it } }

No comments:

Post a Comment